7 research outputs found
Long-time dynamics of Rouse-Zimm polymers in dilute solutions with hydrodynamic memory
The dynamics of flexible polymers in dilute solutions is studied taking into
account the hydrodynamic memory, as a consequence of fluid inertia. As distinct
from the Rouse-Zimm (RZ) theory, the Boussinesq friction force acts on the
monomers (beads) instead of the Stokes force, and the motion of the solvent is
governed by the nonstationary Navier-Stokes equations. The obtained generalized
RZ equation is solved approximately. It is shown that the time correlation
functions describing the polymer motion essentially differ from those in the RZ
model. The mean-square displacement (MSD) of the polymer coil is at short times
\~ t^2 (instead of ~ t). At long times the MSD contains additional (to the
Einstein term) contributions, the leading of which is ~ t^(1/2). The relaxation
of the internal normal modes of the polymer differs from the traditional
exponential decay. It is displayed in the long-time tails of their correlation
functions, the longest-lived being ~ t^(-3/2) in the Rouse limit and t^(-5/2)
in the Zimm case, when the hydrodynamic interaction is strong. It is discussed
that the found peculiarities, in particular an effectively slower diffusion of
the polymer coil, should be observable in dynamic scattering experiments.Comment: 6 page
Laser correlation spectroscopy in an investigation of the subfractional composition of plasma from patients with gastric bleeding, craniocerebral injury, and intoxications
Subfractional composition of blood plasma in benign tumors and breast cancer studied by laser correlation spectroscopy
Medically intractable temporal lobe epilepsy in patients with normal MRI: Surgical outcome in twenty-one consecutive patients
Abnormal MRI findings localizing to the mesial temporal lobe predict a favorable outcome in temporal lobe epilepsy surgery. The purpose of this study is to summarize the surgical outcome of patients who underwent a tailored antero-temporal lobectomy (ATL) with normal 1.5
T MRI. Specifically, factors that may be associated with favorable post-surgical seizure outcome are evaluated.
A retrospective analysis of the Rush University Medical Center surgical epilepsy database between 1992 and 2003 was performed. Patients who underwent an ATL and had a normal MRI study documented with normal volumetric measurements of hippocampal formations and the absence of any other MRI abnormality were selected for this study. Demographic information was collected on all patients. Seizure outcomes were evaluated using Engel's classification. A two-sided Fisher exact test with Bonferroni correction was performed in statistical analyses.
Twenty-one (21) patients met the inclusion criteria of normal 1.5
T MRI and underwent a tailored temporal lobectomy. Mean age at time of surgery was 28
years (SD
=
8.1, range 11–44) and mean duration of the seizure disorder was 13.4
years (range 2–36). Risk factors for epilepsy included head injury (
n
=
4), encephalitis (
n
=
3), febrile seizures (
n
=
2), and 12 patients had no risk factors. Pathological evaluation of resected tissue revealed no abnormal pathology in 12/21 patients (57%). After a mean 4.8
years follow-up post-surgical period, 15/21 (71%) patients were free of disabling seizures (Engel I outcome). At 8.3
years follow-up, 13/21 (62%) patients had similar results. Absence of prior epilepsy risk factors was the only statistically significant predictor of an Engel class I outcome (
p
<
0.0022).
Patients with medically intractable epilepsy and normal MRI appear to benefit from epilepsy surgery. Absence of prior epilepsy risk factors may be a positive prognostic factor